This invention relates to inkjet printers. In particular, this invention relates to novel designs and methods of manufacture of an inkjet printhead capable of printing varying drop-weight quantities of ink.
Inkjet printing mechanisms employ pens having printheads that reciprocate over a media sheet and expel droplets onto the sheet to generate a printed image or pattern. Such mechanisms may be used in a wide variety of applications, including computer printers, plotters, copiers, and facsimile machines. For convenience, the concepts of the invention are discussed in the context of a printer.
A typical printhead includes a silicon-chip substrate having a central-ink aperture that communicates with an ink-filled chamber of the pen when the rear of the substrate is mounted against the cartridge. An array of firing resistors is positioned on the front of the substrate, within a chamber enclosed peripherally by a thin-film layer surrounding the resistors and the ink aperture. An orifice layer connected to the thin-film just above the front surface of the substrate encloses the chamber, and defines a firing chamber just above each resistor. Additional description of basic printhead structure may be found in xe2x80x9cThe Second-Generation thermal Inkjet Structurexe2x80x9d by Ronald Askeland et al. in the Hewlett-Packard Journal, August 1988, pages 28-31; xe2x80x9cDevelopment of a High-Resolution Thermal Inkjet Printheadxe2x80x9d by William A. Buskirk et al. in the Hewlett-Packard Journal, October 1988, pages 55-61; and xe2x80x9cThe Third-Generation HP Thermal Inkjet Printheadxe2x80x9d by J. Stephen Aden et al. in the Hewlett-Packard Journal, February 1994, pages 41-45.
In order to minimize the number of required printheads for a complete printing system and to obviate the need to align separate printheads in a printing system, it is desirable to have the ability to include firing chambers of different drop weights, for example a color column and a black column, on a single printhead. In the past, manufacturers have been unable to make printheads with firing chambers of different drop weights, because firing chambers of different drop weights traditionally required different orifice-layer thicknesses in order to produce the best ink trajectory and drop shape with optimum energy efficiency.
Accordingly, it is an object of the present invention to provide designs for and methods of manufacturing inkjet printheads with firing chambers capable of printing varying drop-weight quantities of ink with optimal energy efficiency and dot shape.
The present invention can be broadly summarized as follows. A substrate has a first-substrate portion with a first-substrate thickness that is thicker than a second-substrate thickness corresponding to a second-substrate portion. A thin-film layer defines a plurality of ink-supply conduits and has a plurality of independently addressable ink-energizing elements. At least one of the ink-energizing elements is aligned with the first-substrate portion and at least one of said plurality of ink-energizing elements is aligned with the second-substrate portion. An orifice layer has a lower-orifice-layer surface conformally coupled to the thin-film layer and an exterior-orifice-layer surface of a uniform height such that the orifice layer has first-orifice portion with a first-orifice thickness that is thicker than a second-orifice thickness corresponding to a second-orifice portion. The orifice layer defines a plurality of firing chambers. Each firing chamber opens through a respective nozzle aperture in the exterior-orifice-layer surface and extends through the orifice layer to expose a respective said ink-energizing element. Each firing chamber is in fluid communication with its respective said ink-supply conduits. At least some of the firing chambers are laterally separated from all other firing chambers by a portion of the orifice layer, such that the firing chambers are not laterally interconnected. By using this configuration, each firing chamber located in the first-orifice portion of the orifice layer that has a first-orifice thickness produces a different-sized drop-weight quantity of ink when its respective said ink-energizing element is energized than each firing chamber located in the second-orifice portion of the orifice layer that has a second-orifice thickness produces when its respective said ink-energizing element is energized.
The inkjet printhead of the embodiment of the previous paragraph can be manufactured by performing the following steps. A provided substrate is etched in order to define at least two substrate areas with different substrate thicknesses. A thin-film layer containing at least one ink-energizing element is applied to the substrate. At least one of the elements is located in each of the substrate areas. A plurality of ink-supplying conduits is etched in the thin-film layer. At least one ink-supplying trench is etched in the substrate in order to provide fluid communication with at least some of the ink-supplying conduits. An orifice layer is applied to the substrate. The orifice layer has an exterior-orifice-layer surface that is substantially planar such that there are at least two orifice areas with different orifice thicknesses that correspond to the two-substrate areas with different substrate thicknesses. At least one firing chamber is formed in each of the two orifice areas in order to provide firing chambers with the capability of producing varying drop-weights quantities of ink.
In another embodiment, the orifice layer has a substantially uniform thickness. However, the orifice layer defines at least two different-sized firing chambers, each having different volumes. Preferably, the larger-volume firing chamber will have a more powerful ink-energizing element that is laterally offset from the firing chamber""s nozzle aperture. And, the smaller-volume firing chamber will have a less powerful ink-energizing element that is aligned with the firing chamber""s nozzle aperture. Thus, in this embodiment, the larger-volume firing chamber produces a larger (i.e. heavier) drop-weight quantity of ink, and the smaller-volume firing chamber produces a smaller (i.e. lighter) drop-weight quantity of ink.
Of course, the printheads, print cartridges, and methods of these embodiments may also include other additional components and/or steps.
Other embodiments are disclosed and claimed herein as well.